The invention relates to a roll of paper or of other similar absorbent material such as a non-woven material intended to be used, for example, for wiping. In particular, it relates to the area of articles for sanitary or household use.
For these applications, the rolls consist of a continuous sheet that may comprise one or several plies, optionally precut into consecutive lengths in the direction of the winding, and rolled axially, preferably about an axis that may either support or not support a core; the roll may also comprise or not comprise a center core. The sheet may be unwound either starting from the external surface of the roll in the direction of the winding or from the interior surface, starting from the center in a direction perpendicular to the direction of the winding of the roll. In this latter case, the roll is said to be a center feed-roll.
The object of this invention is to manufacture rolls that use center unwinding.
When the roll comprises a core, then said core must first be extracted. Generally, the core has been so designed that it can be torn off while pulling on its edge, usually at one of the ends of the cardboard helical spiral that forms it. However, experience has shown that this solution is not always satisfactory, because the extraction of the core sometimes becomes difficult at times if the break-off zone or zones are poorly formed. Furthermore, this action may draw out the first sheets of the roll, which sheets then become difficult to use. Additionally, the first turns of the sheet are frequently glued to the core, making them unsuitable for any type of use and causing them to be discarded as waste.
This core is particularly costly to manufacture, because it is generally composed of two or more layers of cardboard bound by gluing. It is also frequently glued with a “bonding” glue for the first turn of the roll. Furthermore, it is of no use once it is withdrawn and must therefore be discarded as waste.
In order remedy this disadvantage, coreless center-feed rolls have also been proposed. The prior art shows that these rolls are more easily put into service by the user, because it is no longer necessary to remove the core before use. In order to make these rolls, a provisional core may be used, during manufacturing, onto which the sheet may be rolled. The core is then withdrawn before the packaging of the rolls. This technique complicates production at the industrial manufacturing level because it requires the adding of a core removal station to the winding line.
According to one coreless manufacturing process, the sheet is cut on line in the longitudinal direction, before winding, starting from a parent sheet of ample width into as many strips as there are individual rolls to be obtained.
According to another manufacturing process, the parent sheet is rolled directly onto a spindle, also without the insertion of a core. The initial sheet, which is of ample width, is first rolled in such a way as to form one single roll with the definitive diameter of the individual roll, called a “log” in the industry. After the log is formed, the spindle is extracted and the log is cut into sections and then into individual rolls.
However, the sheet, whether made of tissue paper, dry-creped or water-creped, paper by the dry method, or non-woven material, presents a certain elasticity. Owing to the internal stresses of the roll, due for example to the compaction of the sheet onto the spindle during the winding and/or tensioning of the sheet that generates the rolling/unrolling operation by the machine, the reduction of the center opening by the caving in or collapsing at the center of the first turns after the spindle is extracted usually cannot be avoided. This collapsing is produced, for example, after extraction of the spindle and/or at the time of the cutting of the log, by the pressure exerted by the saw.
In any case, a partial or total reduction of the center opening is observed during handling and shipping owing to the inevitable shocks and/or vibrations to which the rolls are subjected.
When the center opening is completely reduced, it is difficult to reshape it with just the hand, and the grasping of the first turn is not easy. Inevitably waste occurs, chiefly when the roll is placed into the dispenser for service, because then the user ends up grasping several turns at once.
It is known from the prior art how to manufacture coreless rolls whose center opening retains its shape after extraction of the spindle and/or after cutting with a saw. For example, a spindle whose profile, grooved or polygonal, can be used, which will permit the formation of an opening whose walls are self-bearing. An exemplary embodiment of this process is disclosed in French Patent No. 2,554,799.
Nevertheless, in this process the diameter of the center opening is small and the first turns are difficult to access. These turns are presented in a tightly-wound, twisted wad with a weak “pitch”, hardly conducive to easy use. If the diameter of the center opening is larger, it is difficult to prevent the first turns from becoming attached to one another. For that, a bonding agent is used that is deposited directly onto the sheet or indirectly by way of the spindle or one of the winding cylinders by an adapted system, at the time of rolling of the first turns onto the spindle. Any other principle of attaching the first turns to themselves, chiefly by a mechanical process, is applicable. Thus, these first turns, which collectively resist the forces of the internal stresses, are consolidated.
However, even still, waste cannot be avoided at the time when the roll is placed into service. Whether in the case of direct use or in the case where this roll is used in a center-feed dispenser in which the end of the sheet is introduced into a relatively narrow dispenser opening, the user is obliged to throw away the first turns that have become attached to one another.
Additionally, in this latter type of manufacturing, it cannot be avoided that certain rolls will not be subject to damage during shipping, with the consequent collapsing of the center opening as in the cases mentioned above. In order to avoid this risk, the rolls should also be packaged, preferably rolls in cardboard cases, in contrast to the rolls with core, for which just a flexible wrapping made of paper or plastic is sufficient. The cost is thereby considerably increased.
Accordingly, the interest that these coreless rolls can generate in relation to rolls with a core is greatly diminished.